Background and importance Increasing bacterial resistance to antibiotics requires new treatment strategies.

Aim and objectives To assess the number and type of pharmacy interventions in therapeutic drug monitoring (TDM) guided piperacillin or meropenem treatments. Treatments were administered by continuous perfusion (CI) in non-critically ill patients.

Material and methods We conducted a prospective study (October 2019-February 2020) to measure plasma concentrations (PC) of piperacillin or meropenem administered by CI. The physician prescribed the antibiotic as a continuous infusion and requested monitoring of drug therapy. The pharmacist established the time to determine PC and interpreted the analytical result, modifying the treatment if necessary. TDM sought to achieve free drug PC with 100% fT, four times the minimum inhibitory concentration (MIC) of the microorganism. If there were no isolates, the MIC of the most resistant microorganism was considered. We used high performance liquid chromatography to determine the PC.

Samples to be analysed were obtained once steady state was reached. The MIC of the microorganisms was determined by microdilution in broth or by E-test. The glomerular filtration rate (GFR) of patients was calculated using CKD-EPI. The pharmacist directly modified the regimen for piperacillin and meropenem PC below 4×MIC or above 6×MIC. Microsoft Excel was used for the statistics calculation.

Results 37 patients treated with piperacillin (62.2% men; aged 67.3±15.4 years) and 11 treated with meropenem (45.5% men; aged 73.8±24.8 years) were included. For 28/37 (75.7%) patients treated with piperacillin and 8/11 (72.7%) treated with meropenem, symptoms related to chronic pulmonary disease were present. We analysed a total of 48 PC for piperacillin and 15 for meropenem. Mean GFR of those treated with piperacillin was 77.46±29 mL/min/1.73 m² and for meropenem 89.27±17.43 mL/min/1.73 m². Pharmacists intervened in 14/37 (37.8%) patients treated with piperacillin, 9/14 (64.3%) to increase the dosage. For meropenem, the pharmaceutical interventions were 4/11 (36.4%), two to reduce the dose. In 90% of the patients in whom the dosage was increased had a GFR >60 mL/min/1.73 m², and 43% of the patients in whom it was decreased had a GFR <60 mL/min/1.73 m².

Conclusion and relevance TDM of beta-lactams shows whether the concentration reached is adequate for the causative microorganism and the patient‘s condition. Pharmaceutical interventions optimised the dosage in cases where standard regimens were not appropriate.

Conflict of interest No conflict of interest